Genetics flash Flashcards
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Restriction fragment lengthpolymorphism (RFLP)
Use restriction enzyme that cuts at specific sequences and measure sequence lengths
Short tandem repeats (STRP)
microsatelite repeats.
Variable number tandem repeats (VNTR)
Minisatelite repeats. Can be detected via MW
Copy number variation (CNV)
Used to detect DNA polymorphisms. All people have same genes, some have extra copies
Single nucleotides polymorphism (SNP)
Single base change. Most common
Automated sequencing
Allows us to build whole genome databases for individuals to provide personalized medicine
Microarray
Oligo nucleotide probes on microarray that bind fluorescently labeled DNA from subject that is complementary. Used to profile gene expression.
Genetic drift
Shift in observed allele frequency from expected from generation to generation due to small population
Founders effect
Subset of genetic drift (small founding population) and some sort of natural selection/ heterozygote advantage
Gene flow
Change of allele frequency due to admixture and migration
Proband
Person from whom the pedigree is initiated
Consanguinity
Mating between related persons
Penetrance
% of individuals that have a certain genotype and express the expected phenotype. (# people with pheno)/(# people with geno.)
Expressivity
Degree to which a genotype is expressed. Variation of severity
Genetic anticipation
Genetic trait is more strongly expressed and earlier in life expressed with each subsequent generation due to increase of triplet nucleotide expansion
Haplotype
Multiple components or loci (ex. A1B1 and A2B2), exhibt linkage
Linkage Disequilibrium
Certain haplotype is more dominant than others, possibly linked to disease while lesser ones are linked
Bad disease marker
Marker segregates randomly, meitotic crossing over
LOD score
Logarithm of odds score. Measures recombination between marker and genetic disease. Lod 3 = 1000:1, significant. Lod -2 is exclusion of marker.
Physical genetic mapping
Use genomic library and genome sequence from human genome project and preform “chromosome walking”
Genetic linkage
Shared within families. Different families have different segments.
Genetic Association
Same variation shared across all families
Epigenetics
Heretible changes in gene expression due to mechanisms other than underlining DNA sequence. Epigenetic marks are erased during gametogenesis/ embryogenesis or linger for 2-3 generations
What nucleotide is methylated
Cytosine
DNA methylation
Transcriptional silencing, protect genome from transposition, genomic imprinting, X inactivation, tissue specific gene expression. Established new every generation
Histone modification
Acetylation, methylation, phosphorylation, ubiquitilation, different histone combinations
Eurchromatin
DNA is unmethylated, histone is acetylated. Transcription on
Heterochromatin
DNA is methylated, histones are deacetylated. Transcription off
HAT
histone acetylase, acetylated histones to make them active
HDAC
histone de-acetylase, deacetylated histones to pack them tightly together
Genomic imprinting
Parent derived chromosomes are epigenetically marked (imprinted = turned off)
Prader-Willi syndrome
Microdeletion of paternal chromosome, maternal chromosome has genomic imprinting. Paternal deletion results in no active genes. Sym: short, mental retardation, hypogonadism, emotional lability, unregulated appetite
Angelman Syndrome
Microdeletion of chromosome that is maternally imprinted. Sym: Microcephaly, seizures, emotional exuberance, attnetion problems, motor problems
Multifactorial disorders
Phenotype is affected by genotype and enviromental factors. Ex: obesity, Diabetes type 2, atherosclerotic heart disease
Threshold model
Underlying genetic liability distribution in population which must be reached for phenotype to be seen
Concordance study in twins
Measure hereitability of disease (1= one twin has it the other twin has 100% chance of having it)
Monozygotic twin
genetically identical
Dizygotic twin
share 50% of chromosome (like siblings)
Enviromental factors
outdoor, indoor, occupational, consumption
Barker hypothesis
Adverse events in fetal life and early childhood establish increased risk of disease in adult life
Sensitivity
Proportion of true positives accurately detected = true positive/ (true pos. + false neg.)
Specificity
Proportion of true negatives accurately detected = true neg./ (false pos. + true neg)
Positive predictive value
Portion of those that are actually positive who test positive = true pos./ (true + false positive)
Negative predictive value
Portion of those who are actually negative that test negative = true neg. / (true + false negative)
Loss of heterozygosity
2nd mutation (often gross event) leading to both alleles being mutated (1st is often inherited or somatic)
Knudsen’s 2 hit hypothesis
1) 1st is inherited, 2nd is gross chromosomal change 2) normal –> very rare 1st event, frequent 2nd event
